By Kelly Whiteside, USA TODAY With three defenders recovering from injury, the center of the USA's defense has become a center of concern. The play of Carlos Bocanegra, Oguchi Onyewu and Jay DeMerit on Tuesday will either ease or intensify the anxiety when the Americans face the Czech Republic in East Hartford, Conn., their first of three exhibitions before the World Cup. "There's no question we have a little situation at center back," Pierre Barrieu, the team's fitness coach, said Sunday. Bocanegra had sports hernia surgery in Germany on May 5. Onyewu hasn't played in a game since last October, when he ruptured his left patella tendon. DeMerit has been battling an abdominal strain. All three are central defenders, though Bocanegra could also play left back. Bocanegra's injury had been listed as an abdominal strain before coach Bob Bradley disclosed the surgery Saturday. Bocanegra said he had been kicked above his left knee in late March while playing for his French club, Rennes. He couldn't flex his knee for three days and said he compensated for the injury by running differently, which caused stress on his lower abdomen. Bocanegra's surgery was performed by Ulrike Muschaweck, the renowned hernia surgeon who developed a technique that cuts recovery time. "It wasn't a big issue," Bocanegra said Sunday. "It's a 15-to-20-minute procedure." Bocanegra said he was running three or four days after surgery. Two weeks after the operation, he was back in full training with the U.S. team. Since camp began last Monday, players have worn heart rate monitors during training so Barrieu could closely monitor their fitness. According to Barrieu, Bocanegra and DeMerit have progressed well. As for Onyewu, the road back to game fitness is a bit steeper. "Gooch is someone who, let's face it, hasn't played a game in seven months," Barrieu said. "We try to give him everything we can, the intensity, the work volume, and he looks like he's doing pretty well." Princeton offense: At times, soccer may seem like a version of Pete Carril's Princeton offense — low scoring, lots of passes — and on Friday the two converged when the legendary basketball coach visited training. "When I was here, I was a young coach," said Bradley, who coached the Tigers from 1984-95. "I watched his teams practice. I watched their games. I knew where to go after basketball games where he would show up. When you're around someone who has that experience, who has wisdom, to pick up a little bit of it, I think is really important." Bradley learned more than just backdoor cuts from Carril. "The thing about Pete, normally in a conversation with someone, you say 'A' and they say 'B.' Then it keeps going," Bradley said. "I found out from Pete early on, I would say 'A' and he would say maybe 'W.' When you're a young coach and you come in contact with people who see things differently, that's important." After the team wrapped up its last training session in Princeton on Sunday, Bradley thanked his alma mater. "It's a great place to get started," he said. He is expected to announce the 23-player World Cup roster midweek before the team meets Turkey in Philadelphia on Saturday. Source: www.usatoday.com